Humidity calibration instrument



FIG. 1 is a top perspective view of a humidity calibration instrument showing my new design;

FIG. 2 is a bottom perspective view of the humidity calibration instrument in FIG. 1 ;

FIG. 3 is a top view thereof;

FIG. 4 is a bottom view thereof;

FIG. 5 is a left side view thereof;

FIG. 6 is a right side thereof;

FIG. 7 is a front view thereof; and,

FIG. 8 is a back view thereof.

Broken lines in the drawings are for illustrative purposes only and form no part of the claimed design. 

CLAIM The ornamental design for the humidity calibration instrument, as shown and described. 